A related-art image forming apparatus performs image adjustment to prevent producing position and density deviation of an image. As an example of a procedure of the image adjustment, the image forming apparatus forms a resist pattern that is a mark used for the position adjustment for each color, obtains a deviation amount (correction amount) between the resist pattern of a basic color and the resist pattern of a test color, and corrects the position deviation of the image of the test color according to the correction amount. In addition, for example, the image forming apparatus forms a density pattern which is a mark used for the density adjustment, obtains a deviation amount (correction amount) between the density of the density pattern and a target density, and corrects the density deviation of the test color according to the correction amount.
However, it is well known that it takes time to obtain the correction amount used for the image adjustment, causing low printing efficiency. Furthermore, if the marks used for the image adjustment are frequently created, consumables (such as toner) will be wasted. In view of this problem, related-art discloses a technology in which whether the printing is monochrome printing or not is determined, and when it is determined that the printing is monochrome printing, the marks used for the image adjustment are not formed.
However, the related-art image forming apparatus has the following problems. That is, there are times when necessity to perform the image adjustment is low, even if the printing is color printing. For example, for text image data in which there are some red characters (not mixed with another color) among black characters, even if the image is a color image, the necessity to correct the position deviation and the density deviation is low. However, the related-art image forming apparatus forms the marks used for the image adjustment as long as the printing is color printing.